This invention relates to a device for determining the dash number size of standard O-rings.
O-rings have long existed in a wide variety of sizes of varying thicknesses and varying diameters. However, a few years ago the United States Department of Defense, in order to standardize O-rings for its own use, issued a standard size catalog which classifies all the O-rings concerned into five categories of section thickness and into approximately 350 different individual sizes, depending not only on the thickness but also on the diameters of the O-rings. It has thus become possible by use of these standard sizes to determine an O-ring size of any standard device and to obtain a replacement by properly measuring the O-ring.
However, since there are some 350 individual sizes of standard O-rings all identified by what is known as the "dash number" under AS-568 series, these sizes do require measurement. People in the field do not often have calipers available suitable for this and even then they would have to have a chart to show what the calipers meant. Accordingly, it has taken a considerable time for a maintenance man to determine the size and then for a parts supply man or stock man to convert that size into the actual catalog dash number under which the O-ring is found. Guesswork selections are, of course, time-consuming and result in costly equipment malfunctions if the wrong selection should be made; so it is important to have the right selection and have it quickly. Several devices have been proposed for doing this, but they have generally been incomplete or have required too many pieces or have had other similar disadvantages.